In known throttle valves, the gates are bodies that can move between a closed position and a maximally open position of a pipe for selective control of the flow rate of fluid through said pipe.
It is obvious from the above that the effectiveness of the gate is directly dependent upon the adhesion achieved between the edge portion of the gate itself and the pipe walls. In order to achieve effective adhesion between the pipe walls and the edge of the gate, the edge of the gate must itself be constituted by a material that is capable of compensating for the dimensional errors and variations that arise over the service temperature range of the gates.
Gates produced from metallic material and machined by specific processes that permit elevated dimensional precision are known. Such a solution has the disadvantage of being particularly costly and, over time, of not having the required levels of effectiveness.
Another known solution provides for the production of a gate constituted by a central supporting portion produced from thermoplastic material and an edge portion produced from thermoplastic elastomeric material and connected to the central body in purely mechanical manner. Such a solution comprises both the disadvantage relating to the geometric constraints imposed by the mechanical connection and the disadvantage relating to the progressive detachment that, as time passes, occurs between the central supporting portion of thermoplastic material and the edge portion of thermoplastic elastomeric material.